MCW: Best Detective Movie
Inside Man, I suspect the pedantic will argue is more Thriller than Cop Movie. However, it's about a couple of hostage negotiators, the fabulous Denzel and Chiwetel, trying to save hostages in a bank from Clive and having to deal with the shark-like Jodie along the way.
It has a fabulous cast, the dialogue is sharp, you know there's a twist in the tale and you can't wait for the reveal. Plus, the music is fantastic.
It's one of my favourite rainy-day movies.